Until recently, a woman, upon discovering that she had contracted breast cancer, had only one avenue open--mastectomy. Often, she would forego this radical surgery because of its traumatic consequences and the cancerous growth would continue unabated. Now, fortunately, victims of cancer particularly breast cancer may opt for an alternative, less drastic treatment. This revolutionary approach has been denominated interstitial brachytherapy and entails the temporary implantation of small particles of radioactive isotopes called seeds, in and around the cancerous tissue.
Interstitial brachytherapy had its genesis in 1901, shortly after the discovery of radium, when the Curies suggested that a small radium tube inserted into a tumor might produce beneficial consequences. The early pioneers in this area followed this suggestion but these crude methods required bulky radium tubes that were difficult to handle. In 1914 the technique was improved by the use of pure radium sulfate and the manufacturing of radium needles with steel or platinum. A similar method took advantage of the relatively short half-life of radon by collecting the gas in tiny glass tubes which were then inserted into the tumor for an indefinite period of treatment. However, it was soon discovered that the bare tubes produced necrosis due to the beta radiation emitted. One attempt to alleviate the harmful presence of beta radiation was to surround each glass tube with a few millimeters thickness of a bismuth paste. While this constituted some improvement, it was not until the radon was collected in gold capillary tubes instead of glass that there was successful filtration of these rays.
During the early 1920's it was discovered that certain types of cancers could be treated more effectively by radium needles of low intensities applied for a 6- to 10-day period. This produced good results in treating intraoral cancers. Later, rules were formulated which permitted a sound distribution of radium throughout the tumor and they enabled the radiotherapist to achieve a uniform dose within a .+-.10% range. Recently, radium substitutes have been developed and incorporated in the treatment and computerized dosimetry has become prevalent. Alternatives to radium that have received widespread implementation include Radon-222, Gold-198, Iridium-192, Iodine-125 and Cesium-137.
Interstititial implantation is chosen as the treatment where the cancers are not resected and where they are not so widespread, fast-growing or so highly radiosensitive to make external X-ray therapy or chemotherapy preferable. Interstitial brachytherapy can frequently be combined with other methods of treatment. It may be used in conjunction with surgery for implantation into a residual tumor, or with intracavity injection of radioactive material in intrathoracic and intraabdominal tumors. It also may be used with external radiation therapy. It often has been found that where part of the tumor is amenable to resection, the patient should undergo resection followed by implantation in the residual tumor. However, it is sometimes preferable to leave even an easily resectable tumor mass as a carrier for an implant.
Two types of implantation are possible--temporary or permanent. The temporary implant provides better control over the distribution of the radioactive sources and the dose. The temporary implant may be adjusted within wide limits after the implantation by the removing of radioactive sources at different times. Permanent implants are desirable for treating tumors in the abdominal and thoracic cavities.
Interstitial brachytherapy has been quite useful in the treatment of breast cancer. The implantation of radium needles covering the breat tumor, axilla, supraclavicular and intercostal spaces was described as early as 1935 by R. G. Hutchinson (Paterson, R. The Treatment of Malignant Disease by Radium and X-ray, Williams & Wilkins Co. (1st Ed. 1957)). This technique had to be abandoned, however, in view of the high incidence of brachial neuritis. A more limited radium implant for small breast tumors fixed to the chest wall was considered as an alternative to X-ray therapy.
The advance of megavoltage, external beam therapy following World War II, combined with a greater consciousness of the effects of radiation exposure, decreased the popularity of implants. However, interest in this form of treatment has undergone a resurgence as a means of avoiding radical surgery in some instances.
In examining the feasibility of employing interstitial brachytherapy, the size of the tumor must be considered. Where, for example, the breast tumor is relatively small, usually less than 4 cm., the doctors first excise the growth in a lumpectomy, a simple surgical procedure. Because removal of larger tumors would destroy the shape of the breast, these are left in place. Interstitial brachytherapy begins by pushing several hollow steel needles horizontally into the breast through the tumorous area so that they surface on the opposite side. Thin plastic tubes are threaded through the needles and anchored in place by small plastic buttons at either end. The radioactive material embedded in a thin nylon ribbon in the form of tiny seeds has been given a sheathing of, for example, stainless steel, platinum or tantalum to block dangerous ionizing beta rays but it permits the release of high energy gamma rays that will destroy the tumor. Preferably, the radiation treatment continues for three to five days. Similar techniques have been employed in treating other tumors as well, for example, those occurring in lips, oropharynx, retromola, trigone, base of the tongue and the palate.
While interstitial brachytherapy has made great inroads in cancer treatment and has become quite prevalent, some difficulties have been encountered in its operation. One of the prime problems faced relates to the recovery of the implanted radioactive seeds from the nylon ribbon. These seeds are generally expensive and it is advisable that they be reused whenever possible. While removal would not ordinarily engender any major difficulty, their radioactivity presents a handling problem.
The seeds may be inserted in the nylon ribbon by hand if they are not radioactive or by a suitable mechanical means. However, once they become radioactive, the removal of the seeds from the nylon by manual means is not possible because it subjects the technician to a prolonged exposure to deletorious rays. Mechanical means of removal do not solve the problem as they do not have the dexterity necessary for handling these small materials. It has been found that dissolving the nylon in a solvent to separate the seeds is also inadequate as the nylon forms a goopy mass further embedding the seeds rather than freeing up the seeds.